Frequency multiplier having an output of pulse groups



Sept. 27, 1949. J. F. GORDON 2,482,974

FREQUENCY MULTIPLIER HAVING AN OUTPUT OF PULSE GROUPS Original Filed April 30, 1946' OSCILLATOR io PULSE 35 FORMING 5 cmcurr MNWWVWW 34 R.F. vloso R.F. OUTPUT l6 AMPLlFlER AMPLIFIER l 2 DELAY cmcun i 5'2 5 4 OSCILLATOR 7 MP n 1LU 11 PULSE PULSE vlDEO GROUPS SZSR? AMPLIFIER OUTPUT I I DELAY cmcun v z I BLOCKING I 4 cmcun 3g 24 7 3mm JAMES F. GORDON Patented Sept. 27, 1949 James F. Gordon, Towson, Md., assignor to Ben dix Aviation Corporation, Towson, Md., a corporation of Delaware Original application April '30, I946, Serial No. 665,957 Divided and this application July. 3, 1947,.Sb1'ial No. 758,960

4Claims. ((1250-27) This invention relates to frequency multipliers and more particularly to multipliers adapted to the multiplication of narrow pulses at a stable repetition rate, and is a division of my application Serial No. 665,957, filed in the United States Patent Oflice on April 30,. 1946.,

In previous practice the multiplication of frequencies has been subject to various Limitations and defects. Some methods are limited to doubling so that a large number of stages are neededto provide any extended factor of multiplication. When power requirements must be met. by an amplifier used selectively as amplifier, doubler,v or tripler,. then methods of regulationmust be added:v to provide the proper output for the. selected condition of operation. In cases: where power is not a requirement. other higher harmonics of an oscillator or amplifier may be selected: and amplifled, but then only of a somewhat limited order. In any such situation where harmonic distortion, selection, and amplification are used, the problem of isolation of the desired harmonic from the many spurious oscillations and unwanted-harmonics is not an easy one nor is it usually favorably accomplished.

Anobject of this invention is to provide a means of frequency multiplication inwhich the desired factor of multiplication be readily obtained without recourse to a large number of .iultiplyi ng channels. 7

Another object of this invention is to provide a means of frequency multiplication by which a large number of available frequencies are readily selectable from one stable oscillator source;

a means of'frequency multiplication in which un-i wanted harmonics and spurious oscillations are not present't'o be amplified by the succeeding. stage or stages.

Another object of this invention is to provide a means of frequency multiplication in which selection of pro-setfrequency is readily accomplished, both in calibration and operation, with a minimum of adjustment and control: devices.

Still another object of this invention is to provide a means of frequency multiplication with'ganjoutput of. short pulses at a definite repetitionv rate,, and which means of. multiplication reflective:- ly lends itself to-further' control, to provide an output of regular,, successive groups of two or more pulses. I Y Other objects and advantages of the invention will become apparent from a considerationof the following specification when taken inconjunctionwith the accompanying drawing, in

which; a

Fig. l is a block diagram showing a multiplying circuit embodying the invention, in relation to its input-output, and tuning means; and,

Fig. 2 is a block diagram showing a modified form of the circuit of Fig. 1 inwhich the multiplier lends itself to the; control of a blocking oscillator to provide an output of regular groupsof pulses.

In- Fig. 1 the output of an oscillator in is connected by a lead. H to a pulse fornr imgv circuit 14 which combination supplies the pulse input energy required by the invention. The output of the pulse formingcirc'uitl4, is-connected. by a,

lead it to the input of a video amplifier 20. The

A further object of this invention is to provide outputiof the amplifier, 2 0 is fed by a lead 22 to a delay circuit 24, and from said delay circuit by a lead 26 back to the: input of amplifier 20.

Connected into the anode circuit of the amplifier 7 2c bytwo leads I8 is a current meter 30. Representing one use of this invention, the output from amplifier 20 is used by connector 32 to drive and control a radio frequency amplifier 34, which is preferably .a tuned, class-C amplifier. The output tank circuit 4250f the amplifier 34 comprises a coil 46 and a variable condenser 44, which may be ganged for tuning purposes with variable condensers 52 and 54 which control the delay applied by the delay circuit 24.. The ganging means is indicatedby the dashed line 50'.

' In operatiomthe' oscillator III, which is preferably crystal controlled for stability, provides the fundamental operating frequency. To provide the: pulsed output needed for. the present means of frequency multiplication, the fundamental oscillation frequency'having a wave-form indicated. by the graph l I is fed to the pulseforming circuit !4-, the output of which consists of very: narrow pulses as shown by graph. t5; having a regular *repetition rate established by the oscillator to.

fier zathe amplified pulse will be an tome delay circuit 24 and again to the input 18 of said amplifier, where the delayed pulse will again be amplified and will follow the initial pulse by an interval equal to the delay time of the delay circuit 24. The second pulse will again be fed to the delay circuit 20 and back to the input 18 of the amplifier 20 Where it will be amplified and will follow the other two pulses by an interval equal to the delay interval between the first two pulses. Such action is started by each pulse from the pulse forming circuit l4.

If the delay circuit 24 is set so that the delay time is 90 of the frequency cycle time of the I output of oscillator 10 then three pulses will follow the initial pulse through the video amplifier I8 before the arrival of the next pulse from the pulse forming circuit I 4. This pulse will occur in step and identify itself with the fourth fedback pulse which is 360 behind the initial pulse to pass the amplifier 20. The output of amplifier 20 will now have a wave-formsuch as indicated by the graph 33.

Under these conditions it can be seen that the output of said video amplifier consists of four times as many pulses per second as are present in the pulse source from the pulse forming circuit [4. If the delay circuit 24 were set for a delay of 120 of the fundamental frequency cycle, then the pulse frequency at the output of the video amplifier would be three times that of the initial frequency from the pulse forming circuit. If the delay were set at 45, then the frequency at the, output of the video amplifier would be eight times the initial frequency. Such multiplication could continue up to the limits of the pulse width and the capabilities of the delay circuit 24.

'With a current meter 30 inserted in the plate circuit of the video amplifier 20, proper adjustment of the pulse delay interval can readily be discerned by the occurrence of a dip in the meter reading'as thedelay interval becomes an integral sub-multiple of the original pulse interval. If the delay circuit were set for a value of 95 delay instead-of a desired 90 behind the preceding pulse the fourth pulse fed-back by the delay circuit would not coincide with the next recurrent fundamental frequency pulse. In a short time, due to this discrepancy, the video amplifier output would consist of a great many random components all of which would add working time to the video amplifier and would be indicated by the meter because of added current. Should the delay circuit be adjusted so that the delay time Would be the desired 90 instead of 95, then the definite dip shown by the plate current meter would indicate that the video amplifier would be working the minimum time of four pulses per fundamental frequency cycle.

With such a plate current indicating device dips would occur with delay time settings of 180, 120, 90", 72, 60, 45, 30, or of any other delay time which will constitute an integral sub-multiple of the pulse interval of the output of the pulse forming circuit l4. As stated above the pulse Width and the capabilities of the delay circuit provide a limitto frequency multiplication which may be attained.

' In using a mutiplier constructed in accordance with this invention to drive a class C radio frequency amplifier such as 34, the anode circuit of said R. F. amplifier is tuned to a resonant frequency comparable to the repetition rate of the multiplied pulses driving its grid. Radio frequency energy of controlled frequency in then available in the anode circuit of the class C amplifier as indicated by the graph 35. The anode tuning of this amplifier 34 and the delay time adjustment of the delay circuit 24 can be mechanically coupled as indicated at 50, to provide a controlled output of a great number of multiples of the frequency of the source oscillator Ill.

The pulsed output of the multiplier can be used to provide precision markers for a time base, since the oscillator Hi can be very stable and the delay conditions may be readily and accurately determined by use of the anode current meter 30.

The circuit illustrated in Fig. 2 differs from that of- Fig. 1 in that a blocking circuit 40 is inserted between the pulse forming circuit l4 and the delay circuit 24. The output of the pulse forming circuit I4 is fed to the blocking circuit 40 through lead 42 andthe blocking circuit is connected to the delay circuit 24 by lead 38 in a manner to renderfeed-back circuit of which the delay circuit is a part inoperative during the blocking interval. The blocking circuit may be any one of a number of well known trigger circuits or synchronized multivibrator circuits.

In the operation of the. embodiment illustrated in Fig. 2 the blocking circuit 40 operates to render the feed-back circuit 22, 24, 2B inoperative for a controllable period of time during each pulse interval of the output of the pulse forming circuit i4. By this means pulse groups of two or more pulses can be producedsuch as indicated by the graph 3?. Variations of pulse grouping can be obtained-by proper control of the operating in-- tervalof the blocking circuit 40.

It will be evident from the foregoing that the invention is not limited to the specific circuits and arrangements of parts shown anddisclosed herein for illustration but that the underlying concept and. principle of the invention-are susceptible of numerous variations and modifications coming within" the broader scope and spirit thereof as defined by the appended claims. The specification and drawing are accordingly to be regarded in'an illustrative rather than a limiting sense.

I claim: r

1. A frequency multiplying system comprising a source of energy pulses; means amplifying the output of said source; means feeding back energy from the output of said amplifying means to the input thereof, said feed-back means comprising means delaying said energy by asub-multiple of the pulse repetition rate of the output of said source, and means rendering said feed-back means inoperative during a portion of each pulse interval of the output of said source.

2. A frequency multiplying system comprising a source of energy pulses, .means amplifying the output of said source, means feeding back energy from the output of said amplifying means to the input thereof, said feed-back means comprising means delaying said energy by a sub-multiple of the pulse repetition rate of the output of said source, and a blocking circuit synchronized with the output of said source and operating to intermittently block the action of said feed-back means. V

3. A frequency multiplying system comprising a stable pulse oscillator, a video amplifier connected to amplify the output thereof, a feed-back circuitfeeding energy from the output of said video amplifier to the input thereof, a delay circuit forming a part of said feed-back circuit and operable to delay the energy'fed back thereby, by an integral subemultiple of the pulse repetition rate ofsaid oscillator output,and a blocking circuit synchronized with said oscillator and consaid feed-back means comprising means delaying 1 said energy ;by an integral sub-multiple of the pulse repetition rate of the output of said source, and means rendering said feed-back means inoperative during a portion of each pulse interval of the output of said source.

JAMES F. GORDON.

REFERENCES CITED The following references are of record in the fileof this patent:

5 V UNITED STATES PATENTS Number Namev Date 2,145,332 Bedford Jan. 31, 1939 2,212,173 Wheeler et al Aug. 20, 1940 10 2,429,227 Herbst Oct. 21, 1947 

